1. Technical Field
The present invention relates to blade mounting devices that permit a blade to be easily and reliably attached to a machine tool, such as a reciprocating saw or a jigsaw. Such blade mounting devices are also known as keyless or tool-less blade clamps or clamping systems for attaching a saw blade to a reciprocating saw.
2. Description of the Related Art
A known tool-less blade clamp for reciprocating saws is disclosed in the U.S. Pat. No. 5,575,071, which is reproduced herein as FIG. 13. The known blade mounting device 30 includes an axially reciprocating rod 31 driven by a motor, a blade lock operation sleeve (clamp collar) 32 rotatably attached to the end of the rod 31 and a torsion spring 34 that biases the blade lock operation sleeve 32 toward a blade clamping position. The blade 35 is inserted into a slot 31a having a uniform width and cross-section. A bearing support hole (aperture) 31b also is formed at the end of the rod 31 and a ball or bearing 33 is disposed within the bearing support hole 31b. The inner surface of the blade lock operation sleeve 32 has a cam face with a gradually varying internal diameter. The bearing 33 is supported between the cam face and the bearing support hole 31b. A guide or stop pin 36 is disposed within a slot 32a that is radially disposed within the blade lock operation sleeve 32. The blade lock operation sleeve 32 rotates about the rod 31 within the range in which the guide pin 36 can move within the slot 32a. 
In order to mount a blade, the blade lock operation sleeve 32 is manually rotated toward a blade release position against the biasing force of the spring 34. As a result of the manual rotation, the bearing 33 moves to the large-diameter side of the cam face and thus moves away from the slot 31a. Therefore, the base of the blade 35 may be inserted into the slot 31a. When the base of the blade 35 is inserted into the slit 31a and the blade lock operation sleeve 32 is not restrained by the operator from returning to the blade clamping position, the blade lock operation sleeve 32 rotates toward the blade clamping position due to the biasing force of the spring 34. As the sleeve 32 reaches the blade clamping position, the bearing 33 is pressed toward the small-diameter side of the cam face. Therefore, the bearing 33 is pushed into the support hole 31b and protrudes from the slot 31a. The bearing 33 thereby lodges within a blade lock hole 35a of the blade 35 and the blade 35 is secured to the rod 31.
According to the known blade mounting device 30, the sleeve 32 must be manually held in the blade release position when the blade 35 is being inserted or withdrawn from the sleeve 32. Thus, the blade insertion and withdrawal operations require the operator to manually hold the sleeve 32 in the blade release position with one hand and insert or withdraw the blade 35 with the other hand. This requirement present a danger that the operator will be injured by the saw blade, because it can be difficult to change saw blades while firmly holding the sleeve 32 at the same time. The blade mounting devices of Japanese Patent No. 2000-117534 and WO 97/31745 also appear to share this problem.
U.S. Pat. No. 5,946,810 teaches a blade mounting device (chucking tube) that can be locked in the blade release position in order to overcome this problem. However, the chucking tube of the ""810 patent must be axially displaced relative to the reciprocating rod along a threaded portion in order to tighten the blade within the blade mounting device. That is, the blade mounting device of the ""810 patent can not utilize a ball or bearing to firmly secure the saw blade to the rod along a longitudinal face of the saw blade and the saw blade receiving slot. Instead, the blade mounting device of the ""810 patent only supports or fixes the blade at the outermost tip of the blade and along a peripheral edge of a pair of lugs that extend perpendicularly from the longitudinal face of the saw blade. Because the saw blade is not supported along the longitudinal face of the saw blade, the saw blade can wobble or shake during a cutting operation. Further, the blade mounting device of the ""810 patent can not be utilized with standardized saw blade designs and can only be utilized with a saw blade having the pair of lugs formed on the shank portion of the blade. Moreover, even though insertion of the saw blade will release the chucking tube from the blade release position, the operator must still manually rotate the chucking tube in order to clamp or fix the blade within the chucking tube. In fact, the operator must manually rotate the chucking tube while pressing the saw blade inwardly against the biasing force of a compression spring in order to ensure that the saw blade is securely fixed.
Consequently, there is a long-felt need for a blade mounting device that can conveniently and reliably attach a saw blade to a reciprocating rod.
It is, accordingly, one object of the present teachings to provide improved blade mounting devices. For example, improved blade mounting devices may have a relatively simple structure and preferably permit the blade to be easily mounted on or withdrawn from the machine tool, such as a reciprocating saw. The improved blade mounting device also may firmly support a longitudinal face of the saw blade in order to prevent the saw blade from wobbling or shaking during a cutting operation. Moreover, improved blade mounting devices preferably can be utilized with saw blades having standard universal designs.
In one representative embodiment of the present teachings, a blade mounting device may include a blade lock operating member, a blade lock control member and a blade lock. The blade lock operating member preferably moves between a blade clamping position and a blade release position. The blade lock operating member may be normally biased towards the blade clamping position. The blade lock control member preferably moves between a blade lock preventing position and a blade lock permitting position. The blade lock control member prevents the blade lock operating member from moving to the blade clamping position when the blade lock control member is located at the blade lock preventing position. Further, the blade lock control member permits the blade lock operating member to move to the blade clamping position when the blade lock control member is located at the blade lock permitting position. The blade lock control member is pushed and moved from the blade lock preventing position to the blade lock permitting position by the blade when the blade is inserted to the rod. The blade lock securely clamps or attaches the blade to the rod when the blade lock operating member moves to the blade clamping position.
In another aspect of the present teachings, the blade lock operating member can move to the blade clamping position when the blade lock control member is in the blade lock permitting position. Further, the blade moves the blade lock control member when the blade is inserted into the rod. Because the blade lock control member moves to the blade lock permitting position due to the insertion of the blade into the rod of the machine tool, the blade clamping operation can be easily performed without requiring a special operation of the blade lock operating member.
In another aspect of the present teachings, blade mounting devices may include an L-shaped slot. A pin may be received within the L-shaped slot. The pin may travel along one portion of the L-shaped slot to change the blade mounting device from a blade clamping position to a blade release position. The pin may then move along the other portion of the L-shaped slot in order to lock the blade mounting device in the blade release position. Therefore, the blade mounting device can be locked in the blade release position in order to permit the operator to change saw blades without being required to manually hold the blade mounting device in the blade release position.
In another aspect of the present teachings, blade mounting devices may include a camming surface that pushes a pressing member, such as a pin or a ball, against the longitudinal face of the saw blade, when the blade mounting device is in the blade clamping position. By pressing and firmly supporting the longitudinal face of the saw blade during the cutting operation, wobbling or shaking of the saw blade during operation will be minimized.
In another aspect of the present teachings, blade mounting devices are taught that do not move along the longitudinal axis of the reciprocating rod when the blade mounting device is rotated from the blade clamping position to the blade release position.
In another aspect of the present teachings, blade mounting devices are taught that have a saw blade receiving slot. A control member, which for example may be a substantially wedge shaped object or a substantially cylindrical object, may be slidably supported within the saw blade receiving slot between a forward position and a rear position with respect to the rod. A biasing member, such as a compression spring, preferably biases the control member towards the forward position. The control member is preferably designed to abut the saw blade when the saw blade is inserted into the saw blade receiving slot. Further, the control member may be further designed to automatically shift the blade mounting device from the blade release position to the blade clamping position when the saw blade is pushed deeper into the saw blade receiving slot against the biasing force of the biasing member. Thus, the operator is not required to manually return the blade mounting device to the blade clamping position after inserting the saw blade.
In another aspect of the present teachings, blade mounting devices are taught that have means for clamping the blade within the blade mounting device by pressing a longitudinal face of the saw blade and means for locking the blade mounting device in the blade release position. The means for clamping the blade in the blade clamping position may be a pressing member, such as a ball or pin, or may be any other structure that fixedly supports the longitudinal face of the saw blade. The means for locking the blade mounting device in the blade release position may be, for example, a pin and slot structure, although a variety of structures may be utilized to perform this function. Thus, in this embodiment of the present teachings, blade mounting devices are taught that can conveniently and reliably secure a saw blade to a machine tool.
Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.